For most air travelers, turbulence provides nothing more serious than the odd moment of extreme panic, but it costs airlines hundreds of millions of dollars each year in injury compensation and aircraft damage. There are various different types of turbulence, but the most dangerous, because it is invisible and extremely difficult to detect, is clear-air turbulence (CAT). A new CAT detection technology that could help pilots choose a smoother route is now being tested as part of a European joint project called DELICAT (Demonstration of LIDAR based CAT detection).